This invention relates to agricultural implements in general and more particularly to a guidance system and method for steering a mobile farming implement along row mark or other identifying markings on the surface of a field.
It is necessary in many farming operations for the operator of a mobile farming implement to traverse a field in equally spaced apart swaths. For example, during planting the farmer must plant in adjacent swaths with constant space between adjacent rows so that during cultivating the cultivator teeth can be easily and consistently guided to engage the ground between the growing plants. Conventionally row markets are pivotally attached adjacent both outer edges of a planter which comprise elongated arms adapted to be alternately raised and lowered with each having a blade or other suitable device at the distal end thereof for tracing a row mark on the surface of the field. The row mark represents the position for the center line of the tractor or one of its steering wheels when the operator turns the tractor 180.degree. to plant, or bed rows in the opposite direction.
As the vehicle operator makes one swath through the field, he will position one of two row markers which is located on the side of the planter nearest a previously unworked swath so as to leave a mark on the surface of the ground parallel to the path of the implement. At the end of the field the direction of the implement is reversed so as to work the next unworked soil surface and with the tractor pulling the planter following the previous row mark left by the row marker. When the end of the field is again reached, the implement is turned around and the operator will raise the previously lowered marker and lower the opposing marker so as to engage the unworked surface adjacent the swath next to the worked. The planter is again propelled by the tractor across the field with the opposite row marker tracing the untreated surface of the ground as the tractor pulling the planter follows the previous row mark. This alternating process is continued until the field is completely worked.
The row markers are bulky and relatively expensive, and the hydraulic mechanisms for alternately raising and lowering them are complicated. With a twenty-four row planter, the implement width is approximately 60 feet. Thus the row marker must extend approximately 30 feet from each extremity of the tractor. Such row markers present problems. In the elevated position they may engage utility or telephone lines. Also, the operator must stop or slow down the tractor while alternatelty raising and lowering the row markets. Further, due to the length of the markers, unusually high stresses are placed on the pivot members, thereby causing repair problems.
Optical guidance systems are also known for mobile farming implements which visually display information to the implement operator to assist him in steering the vehicle in accordance with identifying markings on the field such as a crop furrow or the boundary between worked and unworked portions of the field. U.S. Pat. No. 4,365,268 to Allen et al discloses a video tractor-planter guidance system wherein a TV camera pivotally mounted at one end of a planter views a row mark created in the soil by a previous pass of the planter, the image of the row mark is viewed by the tractor operator from a TV monitor on the tractor, and automatic control mechanism is provided for adjusting the horizontal angle of the TV camera so it is always aiming in a dirction parallel to the direction of travel of the tractor. U.S. Pat. No. 4,211,921 to Kanetou et al discloses a sensor having means for taking an optical image of the boundary between worked and unworked portions of the field, a plurality of photoelectric elements arrayed in a direction perpendicular the image of the boundary, and camera means for compressing the optical image and projecting it on the array of photoelectric elements so that the position of the implement relative to the boundary can be determined from comparison of the photoelectric outputs from the elements. U.S. Pat. No. 4,288,814 to Talley et al discloses a furrow following optical guidance system wherein a rearward viewing video camera views the area of the ground beneath the vehicle and displays the furrow to the vehicle operator on a video monitor so that he can adjust the vehicle steering wheel to maintain the tire imprint in the middle of the furrow viewed by the TV camera. The disadvantage of such known optical guidance systems is that they view the identifying marking, i.e., the furrow or the row mark or the boundary between and unworked portions of the field, from a single spot only and provide no steering information to the vehicle operator as to the direction of the identifying marking ahead of such single spot.